A helicopter rotor blade has a leading edge at the forward end thereof. The outboard end of the leading edge of the rotor blade travels faster than the inboard portion of the leading edge since the inboard portion is closer to the axis of rotation of the rotor blade than the outboard end. The outboard end of the leading edge of the rotor blade is thus subjected to more abrasion and erosion than the inboard portion due to the faster rotational speeds at which the outboard end travels through air, such that the outboard end of the leading edge will wear much more rapidly than the inboard portion of the rotor blade. To compensate for the increased wear encountered on the leading edges of rotor blades, leading edge abrasion wear strips have been provided on the leading edges of prior art rotor blades. Prior art leading edge abrasion wear strips have been provided by stainless steel, titanium and electroformed nickel components which are mounted to the leading edges of the prior art rotor blades.
Prior art rotor blades have, in the past, been made of metal. Typically, structural components of prior art rotor blades were provided by blade spars, which were made of metal. The prior art leading edge abrasion wear strips were mounted directly to the blade spars, and in some cases, they were adhesively secured. These prior art abrasion wear strips provided erosion protection, extending the service life of the prior art rotor blades. In some cases, the leading edge abrasion wear strips were structural components of the rotor blades.
After a period of time, the prior art leading edge abrasion wear strips became worn due to abrasion and erosion, and required repair. One prior art repair procedure was to provide a supplemental leading edge abrasion wear strip which fit around the exterior of the outboard end of the original rotor blade leading edge abrasion wear strip. Some of these prior art supplemental leading edge abrasion wear strips were electroformed of nickel, by electroplating the nickel onto a mandrel having the same contoured shape as the prior art rotor blade, such that the electroformed nickel abrasion wear strips would fit securely upon the original rotor blade leading edge strips without adversely affecting the aerodynamic performance of the prior art rotor blades beyond acceptable limitations. The supplemental leading edge abrasion wear strips were typically adhesively bonded to metal blade spars. Structural adhesives were used to provide sufficient strength for securing the supplemental leading edge abrasion wear strips to the outboard ends of the helicopter rotor blades in the presence of rotational forces which occur at the high rotational speeds at which the leading edges of the outboard ends of the blade tips of the helicopter rotor blades travel. In the prior art, the supplemental leading edge abrasion wear strips were hot bonded to the prior art rotor blades, utilizing structural adhesives which were cured at high temperatures.
Recent developments in materials technology have resulted in the use of composite materials for rotor blade structural components. These composite rotor blade structural components cannot withstand the elevated temperatures that are required to adhesively bond supplemental leading edge abrasion wear strips to rotor blades using high temperature, hot bond cures. In the past, since prior art rotor blades on which the supplemental leading edge abrasion wear strips were used did not include composite materials, the structural adhesives used for securing supplemental leading edge abrasion wear strips to the rotor blades were hot bonded, by curing within an oven operating at elevated temperatures, which were in excess of 185.degree. F. (85.degree. C.). However, with advanced composite materials, such as fiberglass, carbon fiber, and the like, the rotor blade structural components cannot be heated to the high temperatures required to adhesively secure supplemental leading edge abrasion wear strips to the rotor blade leading edge surfaces using structural adhesives, which are cured with high temperature, hot bond cures.
Other components have been bonded to the aft ends, or trailing edges, of prior art helicopter rotor blades. Such components have been made of materials such as aluminum, and have had structural adhesives precured to the bonding surfaces thereof so that they may be applied in the field without need of cumbersome in-field surface preparation techniques for preparing bonding surfaces, as is typically required for components made of aluminum.